<template>
  <div class="pagination">
    <button :disabled="pageNo == 1" @click="$emit('getPageNo', pageNo - 1)">
      上一页
    </button>
    <button
      v-if="startNumAndEndNum.start > 1"
      @click="$emit('getPageNo', 1)"
      :class="{ active: pageNo == 1 }"
    
    >
      1
    </button>
    <button v-if="startNumAndEndNum.start > 2">...</button>
    <div>
      <button
        v-for="(page, index) in startNumAndEndNum.end"
        :key="index"
        v-show="page >= startNumAndEndNum.start"
        @click="$emit('getPageNo', page)"
        :class="{ active: pageNo == page }"
        
      >
        {{ page }}
      </button>
    </div>

    <button v-if="startNumAndEndNum.end < totalPage - 1">···</button>
    <button
      v-if="startNumAndEndNum.end < totalPage"
      @click="$emit('getPageNo', totalPage)"
      :class="{ active: pageNo == totalPage }"
    >
      {{ totalPage }}
    </button>

    <button
      :disabled="pageNo == totalPage"
      @click="$emit('getPageNo', pageNo + 1)"
    >
      下一页
    </button>
    <button style="margin-left: 30px">共{{ total }}条</button>
  </div>
</template>

<script>
export default {
  name: "Pagination",
  props: ["pageNo", "pageSize", "total", "continues"],
  computed: {
    totalPage() {
      //向上取整
      return Math.ceil(this.total / this.pageSize);
    },
    //连续页码的起始页码、末尾页码
    //计算出连续页码的数字(开始数字|结束数字)【比如:8  6 7 8 9 10】
    startNumAndEndNum() {
      const { pageNo, continues, totalPage } = this;
      //连续页码的开始数字|结束数字
      let start = pageNo - parseInt(continues / 2);
      let end = pageNo + parseInt(continues / 2);
      //还有一些不符合条件的需要纠正数字

      //pageNO 1  2
      if (start < 1) {
        start = 1;
        end = continues;
      }
      //pageNo 32 33
      if (end > totalPage) {
        end = totalPage;
        start = totalPage - continues + 1;
      }
      //当前这个计算属性。需要把开始与结束数字返回，只能返回一个对象
      //底下的对象：KV一致省略V
      return { start, end };
    },
  },
};
</script>

<style scoped lang="less">
.pagination {
  text-align: center;
 
  button {
    margin: 0 5px;
    background-color: #f4f4f5;
    color: #606266;
    outline: none;
    border-radius: 2px;
    padding: 0 4px;
    vertical-align: top;
    display: inline-block;
    font-size: 13px;
    min-width: 35.5px;
    height: 28px;
    line-height: 28px;
    cursor: pointer;
    box-sizing: border-box;
    text-align: center;
    border: 0;

    &[disabled] {
      color: #c0c4cc;
      cursor: not-allowed;
    }

    &.active {
      cursor: not-allowed;
      background-color: pink;
      color: #fff;
    }
  }
}

</style>
 
  